This application relates to a heat exchanger which cools air to be utilized for various uses on a gas turbine engine, and which is relatively compact.
Gas turbine engines are known and typically include a fan delivering air into a compressor section. The air is compressed and passed into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
The fan also delivers air into a bypass duct which does not travel to the compressor, but instead provides propulsion as it exits the engine. A cold coldest source of air on a gas turbine engine is this fan bypass air.
Historically, the fan rotated at the same speed as a compressor rotor. However, more recently, a gear reduction has been placed between the two such that the fan rotates at slower speeds. With this, the diameter of the fan can increase, and a bypass ratio, or amount of air delivered into the bypass duct compared to the volume of air delivered into the compressor section also increases.
As can be appreciated, there are challenges with design and operation of a gas turbine engine. In particular, the turbine section is exposed to very hot temperatures. Thus, high pressure cooling air is typically delivered for various cooling uses, especially in the turbine section. The highest pressure source on the engine would be associated with a downstream location in a high pressure compressor section. However, this air is hot.
Thus, it is known to cool the high pressure air to be used for cooling. Typically, the air has been cooled by bypass air. However, and especially with the use of geared turbofans, the fan driven air in the bypass duct is at relatively low pressure and may not always adequately cool the air to be utilized as cooling air.